The grouping will still be the name of the soruce, and everything after the entire match will be the name of the metric. In this way, the information at the beginning would be discarded. I'll add a unit test for this to clear things up.

Also, the source regex should not match the whole string -- just the beginning  / source part. It's literally everything after the entire match that is used for the metric name -- so that you can discard separators.